From IB-Angel (Internet Brands - owner of QuiltingBoard on another IB owned board whose members also received the quilting email - which is pretty funny.)
"We are aware of the e-mail being discussed. This one-time e-mail was sent in error, and precautions have been taken to prevent an occurrence like this from happening again. Your e-mail address has not been compromised.
We apologize for the inconvenience. "
Earlier, they didn't have an explantion but I guess on further investigation, they found out they were, in fact, the source.
I don't know if the sending of the email to that membership was done at the same time as the one to the QB members.
If you had done a whois on the the link in the original email, it linked right back an IB domain.